Variable inductor with a reinforced coil form



5- A. ADAMS Nov. 28, 1967 VARIABLE INDUCTOR WITH A REINFORCED COIL FORM Filed April 8, 1966 Fig. 3

fan/ey A. Adams I N VE N TOR we; Allameys United States Patent ABSTRACT OF THE DISCLOSURE A tubular body made of a thermoplastic material on which a coil is supported having leads adapted to be soldered to terminals projecting from one axial end of the tubular body. The terminals are fastened to a heat resistant sleeve embedded within an annular cavity formed in the tubular body to hold the terminals in position during soldering.

This invention relates to electronic components adapted to be mounted on printed circuit boards and more particularly to a coil form and coil winding assembly and constitutes an improvement over my prior copending applica tion Ser. No. 523,150, filed Jan. 26, 1966 with respect to which this application in a continuation-in-part.

The coil form construction of the present invention is made of a thermoplastic material such as nylon supporting a coil winding and terminal lug elements to which the winding is soldered so as to establish electrical connections between the coil winding and other components of the printed circuit with which the coil winding is associated. In view of the small size of the coil form and the thermoplastic property of the material from which it is made, some difficulty is experienced in soldering the coil winding leads to the terminal lug elements. It is therefore an important object of the present invention to provide the coil form with a relatively rigid, heat resistant sleeve cooperating with the fastener formations of the terminal lug elements so as to prevent migration of the terminal lugs during the soldering operation.

An additional object of the present invention is to provide a coil form of the aforementioned type having facilities for mounting an axially positioned tuning core protectively spaced from the terminal lugs.

A still further object of the present invention is to provide a coil form construction having coil confining flanges spaced from an enlarged end portion of the coil form body on which the terminal lugs are mounted so as to prevent displacement of the coil winding.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described iand claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIGURE 1 is a top plan view of one type of coil form construction made in accordance with the present invent on with a coil winding mounted thereon.

FIGURE 2 is an end view of the coil form assembly shown in FIGURE 1.

FIGURE 3 is an enlarged longitudinal sectional view taken substantially through a plane indicated by section line 3-3 in FIGURE 1.

FIGURE 4 is a perspective view showing the coil form assembly being adjusted by means of a tool inserted into one axial end thereof.

Referring now to the drawings in detail, a coil form and coil winding assembly generally denoted by reference numeral is shown. The coil form includes an elongated tubular body 12 including a diametrically enlarged end portion 14 at one end 16 opposite the other axial end 18.

3,355,687 Patented Nov. 28, Ififi? The tubular body is made of a thermoplastic material such as nylon and is provided with a pair of flanges 2t) and 22 axially spaced from each other and from the enlarged end portion 14 so as to mount therebetween a coil wind ing 24. The tubular body is also formed with an axial bore 26 of constant cross-sectional dimension. A plurality of circumferentially spaced projections 28 extend axially through the tubular body extending radially inwardly from the internal surfaces of the bore to hold an externally threaded tuning core 30 in an adjusted position. The tuning core may be provided with a non-circular bore 32 adapted to receive one end of a tool 34 as shown in FIGURE 4. In this fashion, the tuning core 34) is rotated by means of the tool so as to axially position the core within the tubular body in order to vary the electrical characteristics associated with the coil winding 24.

The coil winding is adapted to be electrically connected to other components of the circuit with which it is associated by means of the electrically conductive terminal lugs 36. Each terminal lug is mounted externally on the enlarged end portion 14 of the tubular body and projects axially from the end 16 thereof. In one type of terminal lug illustrated, a soldering portion 38 is struck out there from just beyond the axial end 16 of the tubular body so that a lead 40 from the coil winding may be soldered thereto, the leads extending from the coil body through notches 42 formed in the flange 2i) closest to the end portion 14. Also struck out from the terminal lugs are a pair of fastener prongs or formations 44 by means of which the terminals lugs are secured to the tubular body.

As more clearly seen in FIGURE 3, the enlarged end portion 14 of the tubular body is provided with an annular cavity 46 within which is received an annular, heat resistant sleeve 48 preferably made of a phenolic impregnated paper. Thus, the sleeve 48 will retain its relatively rigid physical property under the relatively high temperatures to which it may be subjected while the leads 4d are being soldered to the terminal lugs. Further, the sleeve 48 embeds the gripping ends of the fastener prongs 44 which extend thereinto through the radially outer portion of the enlarged end portion 14 of the tubular body. Thus, the terminal lugs 36 are anchored to the sleeve in addition to the radially outer portion of the enlarged end portion 14, the terminal lugs being spaced from the tuning core 39 by the enlarged end portion 14 on the radially inner side of the sleeve 48. It will be apparent from the foregoing, that although soldering temperatures may exceed the flow point temperature of the thermoplastic material from which the tubular body is made, the fact that the terminal lugs are anchored to the heat resistant sleeve 48, will prevent migration of the terminal lugs during soldering operation. Further, the described arrangement permits the soldering of the lead to the terminal lug at the bottom by a dip soldering method so that one may solder two or more connections at the same time to be terminal lugs. Also, the coil winding assembly may be tuned through the end 16 from which the terminal lugs project without any contact between the core and any portion of the terminal lugs. The described coil form construction also includes the flanges 2t) and 22 by means of which axial displacement of the coil winding 24 is prevented regardless of the handling to which the assembly is subjected.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

n is

What is claimed as new is as follows:

1. A coil form for a coil winding comprising, an axially elongated tubular body made of thermoplastic material including an end portion having an annular cavity formed therein, a heat resistant sleeve with said cavity remaining substantially rigid at the flow point temperature of said thermoplastic material, and at least one terminal element mounted externally on said end portion of the tubular body and projecting axially therefrom, said terminal element having fastener means projecting into the annular cavity and embedded in said sleeve for preventing migration of the terminal element when soldering the coil winding thereto at soldering temperatures exceeding said flow point temperature of the thermoplastic material.

2. The combination of claim 1 wherein said end portion of the tubular body is diametrically enlarged and formed with a bore, a core received within said bore and means threadedly mounting the core Within the bore for axial positioning thereof, said core being radially spaced from the terminal element at the end portion and thermally insulated therefrom by the sleeve.

3. The combination of claim 2 wherein said terminal element includes a soldering portion to which the coil winding is electrically connected adjacent the enlarged portion of the tubular body.

4. The combination of claim 3 wherein said sleeve is made of phenolic impregnated paper.

4 5. The combination of claim 1 including a tuning core threadedly mounted in said tubular body for axial positioning by a tool inserted into the enlarged end portion. 6. The combination of claim 5 wherein said terminal 5 element includes a soldering portion to which the coil winding is electrically connected axially beyond the tubular body.

7. The combination of claim 1 wherein said terminal element includes a soldering portion to which the coil 10 Winding is electrically connected adjacent the end portion of the tubular body.

8. The combination of claim 1 wherein said sleeve is made of phenolic impregnated paper.

15 References Cited UNITED STATES PATENTS 2,648,031 8/1953 Lang 336-436 X 2,929,045 3/1960 Stanwyck 339-220 20 3,071,743 1/1963 Patk-a 336-192 X 3,129,397 4/1964 Scherry 336-136 3,130,381 4/1964 Oeler 336-136X 3,278,877 10/1966 Kameya 336136 LEWIS H. MYERS, Primary Examiner.

E. A. GOLDBERG Assistant Examiner. 

1. A COIL FORM FOR A COIL WINDING COMPRISING, AN AXIALLY ELONGATED TUBULAR BODY MADE OF THERMOPLASTIC MATERIAL INCLUDING AN END PORTION HAVING AN ANNULAR CAVITY FORMED THEREIN, A HEAT RESISTANT SLEEVE WITH SAID CAVITY REMAINING SUBSTANTIALLY RIGID AT THE FLOW POINT TEMPERATURE OF SAID THERMOPLASTIC MATERIAL, AND AT LEAST ONE TERMINAL ELEMENT MOUNTED EXTERNALLY ON SAID END PORTION OF THE TUBULAR BODY AND PROJECTING AXIALLY THEREFROM, SAID TERMINAL ELEMENT HAVING FASTENER MEAND PROJECTING INTO THE ANNULAR CAVITY AND EMBEDDED IN SAID SLEEVE FOR PREVENTING MIGRATION OF THE TERMINAL ELEMENT WHEN SOLDERING THE COIL WINDING THERETO AT SOLDERING TEMPERATURES EXCEEDING SAID FLOW POINT TEMPERATURE OF THE THERMOPLASTIC MATERIAL. 